In the past, electromagnetic actuators, electromagnets, and other devices utilizing the interaction of electrical current and magnetic fields were customarily constructed such that the electrical current would flow in either a copper or aluminum material. This choice of material was based on the fact that copper and aluminum have substantially lower electrical resistivity than most other materials, yet are available at a relatively low cost. The low electrical resistivity is desirable in that, for a given current flowing in a conductor of a given geometry, the rate at which heat is generated is directly proportional to the electrical resistivity. Therefore, the use of copper or aluminum material in the coils is believed to reduce the heat generated and accordingly, reduce the energy lost to the heat. This reduction in heat is generally characteristic of devices having greater useful output per energy expended, and thus greater efficiency.
Many electromechanical devices use ferromagnetic materials to enhance or focus the magnetic fields upon which the device function depends. In these cases, the key property of the ferromagnetic materials is their high magnetic permeability. The magnetic field or flux lines will follow paths of volumes of high permeability. Therefore, the use of the ferromagnetic materials, such as iron, cobalt, nickel, and a wide variety of specialized alloys is also desired.
For a large class of electromagnetic devices, forces are produced by currents that flow in material placed in a magnetic field. In the prior art, ferromagnetic materials were used to guide, focus, and enhance the magnetic fields, and currents were made to flow in materials of low resistivity, such as copper or aluminum. The efficiency of such devices depends on the simultaneous presence of currents and magnetic flux in certain volumes. The insertion of copper or aluminum in these volumes reduces the magnetic flux by large factors from the amount of flux that would exist in an construction entirely of ferromagnetic materials.
Therefore, a need exists for an electromagnetic actuator design that uses ferromagnetic material as both a flux carrier and a current carrier, wherein the disadvantage of the high resistivity of the ferromagnetic material is more than compensated by the flux enhancements.